Method for producing a powder product from a liquid substance or mixture of substances

ABSTRACT

In a process for producing a pulverulent product from a liquid substance or mixture of substances, the liquid substance or mixture of substances to be pulverized is first provided in a pressure vessel. A gas is then dissolved under elevated pressure in the liquid substance or mixture of substances. The resulting liquid/gas solution is then conducted out of the pressure vessel and to an expansion element, through which it is passed and rapidly expanded. Upstream of the expansion element, in the expansion element or downstream, in particular just downstream, of the expansion element, a solid pulverulent auxiliary is admixed. In this manner, a stable pulverulent product results from the solution or from the substance or mixture of substances.

The invention relates to a process for producing a pulverulent productfrom a liquid substance or mixture of substances at ambient temperature.A process of this type is disclosed by WO 95/21688.

Pulverulent products are frequently preferred because of their simplerhandling in comparison with liquids. In the usual case, for example, thetransport and storage of a pulverulent product is less critical thanthat of a liquid. To produce powders, mechanical processes, such asgrinding and agglomeration, and thermal processes, such ascrystallization and spray-drying, are known. Substances which arepulverized by such classical processes generally have a melting pointwhich is significantly above the ambient temperature (room temperature).This means that the physical state of these substances is not changed bythe pulverization.

Substances whose melting point is beneath the usual ambient temperaturecannot be pulverized until they have been solidified by cooling. Evenafter the pulverization, the solid state of such substances can only beretained with the use of complex cold chains. Another possibility forstabilizing substances which are liquid at usual ambient temperature isapplying the substance to be stabilized to finely divided supportparticles. In this case the support particles are fluidized using a gasstream and the liquid substance to be stabilized is sprayed onto thefluidized support particles. By means of this process, which has becomeknown as fluidized-bed coating, the support particles are coated with athin film of the liquid substance to be stabilized. The mass ratiobetween the support and the substance stabilized in this way isdetermined by the dimensions and the shape of the support particles aswell as by the coating thickness. The achievable active ingredientconcentrations (active ingredient is taken to mean here the substancewhich is liquid at room temperature and is to be stabilized) are between1% by weight and at most about 10% by weight, based on the finishedcoated support particles. Furthermore, a coating technique of this typecan only be employed with certain material combinations in which themutual wetting and adhesion forces permit the production of a coatedsupport particle. A further restriction is given by the liquid to bestabilized: if its viscosity is too high, it cannot be sprayed, or canonly be sprayed with great effort. In the case of some liquids, thesprayability can be improved by dilution with suitable solvents, butthis means additional expense and, furthermore, reduces the activeingredient content in the finished stabilized product, quite apart fromthe fact that the use of many solvents is now undesirable fromphysiological and environmental aspects.

The previously mentioned process disclosed by WO 95/21688 makes itpossible to produce pulverulent solids from liquids. The principle ofthe process is to dissolve a gas in the liquid to be pulverized underelevated pressure, preferably until a gas-saturated solution isobtained. In comparison with the pure liquid, a solution of this typehas a number of favourable properties: thus, usually, the viscosity ofthis solution in comparison with the pure liquid at the same temperatureis decreased by several orders of magnitude and the surface tension isalso markedly reduced. The pressurized liquid/gas solution is thenpassed to an expansion element and there rapidly expanded. In the courseof this, the gas present in the liquid/gas solution cools significantly,with great increase in volume, and separates from the liquid. Thisprocess leads to the formation of small solid particles which consistentirely of the substance which was previously liquid. The solidparticles formed can be separated off by conventional processes and, ifdesired, can be fractionated.

Although this known process is an elegant and simple method ofconverting liquids into a pulverulent product, the resulting pulverulentproduct must still be cooled if the melting point of the processedsubstance is below the usual ambient temperature.

The object therefore underlying the invention is to provide a process bywhich substances or mixtures of substances which are liquid at roomtemperature or at ambient temperature can be stabilized in powder form,with the resulting powder form needing to be stable at room temperatureor usual ambient temperature.

This object is achieved according to the invention, starting from theprocess mentioned at the outset, by means of the fact that a solid,pulverulent auxiliary is admixed to the liquid substance or mixture ofsubstances to be pulverized or to the liquid/gas solution upstream ofthe expansion element, in the expansion element or downstream, inparticular just downstream of the expansion element. In the processaccording to the invention surprisingly, even relatively small additionsof auxiliary are sufficient to stabilize the pulverulent product formedon rapid expansion of the liquid/gas solution. In this process, lesssolid auxiliary is required the higher the melting temperature of thestarting substance to be pulverized. Thus, by the process according tothe invention, pulverulent products can be produced which have a highactive ingredient content. This means that in the case of manysubstances or mixtures of substances a comparatively small amount ofauxiliary, for example 1 to 90% by weight, preferably 10 to 80% byweight, and particularly preferably only 20 to 50% by weight, issufficient for stabilizing the resulting powder form. Such high activeingredient concentrations could not be achieved by the processes knownhitherto.

In the expansion of the liquid/gas solution, the temperature may fallbelow the solidification temperature of the substance or mixture ofsubstances, but this is not absolutely necessary in order to obtain thedesired pulverulent product. However, it has proved to be expedient,with a number of applications, during the expansion of the liquid/gassolution, to attain a temperature which is at least in the vicinity ofthe solidification temperature of the substance or mixture ofsubstances.

As gas, in principle, use may be made of any gas which dissolvessufficiently in the liquid substance or mixture of substances to bepulverized. For example, as gas, use can be made of carbon dioxide, ahydrocarbon, in particular methane, ethane, propane, butane, ethene,propene, or a halogenated hydrocarbon, an ether, an inert gas, inparticular nitrogen, helium or argon, a gaseous oxide, in particulardinitrogen oxide or sulphur dioxide and ammonia. A mixture of two ormore of the abovementioned gases can also be used.

The elevated pressure under which the gas is dissolved in the liquidsubstance or mixture of substances can be in the range from 5 bar to 800bar, but preferably the pressure is in the range from 10 bar to 350 bar,and particularly preferably in the range from 20 bar to 250 bar.

Preferably, the dissolution of the gas in the liquid substance ormixture of substances is accelerated by mixing the gas with the liquidsubstance or mixture of substances. This mixing can be achieved, forexample, by shaking or rolling the pressure vessel into which the liquidto be pulverized has been introduced. Alternatively, the solution formedin the pressure vessel can be stirred by means of an agitator. Yetanother possibility for achieving good mixture of the liquid to bepulverized with the gas is to recirculate the liquid phase present inthe pressure vessel and/or the gas phase, i.e. to pump it out of thepressure vessel and to feed it back to the pressure vessel in the areaof the other respective phase. Yet another possibility is the use of astatic mixer. Obviously, the abovementioned procedures can also becombined.

The process according to the invention functions in principle with anysolid pulverulent auxiliary. However, those which are particularlysuitable are auxiliaries having as small a particle size as possible,for which reason, according to a preferred embodiment of the processaccording to the invention, the particle size is less than 100 μm and,in particular, less than 50 μm. Auxiliaries which have a porous innerstructure, whose internal surface area is therefore as large aspossible, are particularly well suited for use in the process accordingto the invention. Examples of substances having a large internal surfacearea which may be mentioned here are zeolites and activated carbon. Ingeneral, a suitable auxiliary is selected according to technical,physiological and also, if appropriate, according to food-law aspects.Without any claim as to completeness, possible auxiliaries which may bementioned here are starch, modified starch, common salt, sugar,proteins, gelatin, titanium dioxide, magnesium stearate, polyglycols,highly disperse silicon dioxide, silicic acid, bentonite, lime,glutamate, emulsifiers, in particular phospholipids or partialglycerides, fats, cellulose and cellulose derivatives, polylactic acid,waxes, dextrin, kaolin, thickeners, in particular alginates or pectin,very finely ground plant components or a mixture of two or more of theabovementioned substances each of which must be present in powder form.

Depending on the liquid substance or mixture of substances to bepulverized, certain auxiliaries are suitable for use in the processaccording to the invention: for example, phospholipids are highlysuitable in principle as an auxiliary for stabilizing the desired powderform. Furthermore, phospholipids are natural highly effectiveemulsifiers both for water-in-oil emulsions and for oil-in-wateremulsions. Phospho-lipids therefore improve the water dispersibility ofoil-soluble substances and the oil-dispersibility of water-solublesubstances. They are therefore used as auxiliary, in particular, ifthese additional properties are of relevance. Poly-ethylene glycol-s,highly disperse silicon dioxide, starch, modified starch and magnesiumstearate are water-soluble or readily dispersible and are solubilizersfor water-insoluble substances. The use of these substances as anauxiliary in the process according to the invention therefore not onlystabilizes, as desired, the powder form, but simultaneously improves thewater dispersibility or water solubility of oil-soluble substances ormixtures of substances.

In the process according to the invention, the auxiliary concentration,based on the total amount of liquid substance or mixture of substancesand auxiliary, is to be as low as possible. Particularly preferably, theauxiliary concentration is therefore only up to 25% by weight. Ifauxiliary concentrations up to 25% by weight are not sufficient tostabilize the previously liquid pulverized substance, preferably, up to50% by weight auxiliary concentration can also be used in the processaccording to the invention. In the case of some liquid substances ormixtures of substances to be pulverized, it may be necessary to choosethe auxiliary concentration even higher, for instance up to 90% byweight. Even this relatively high auxiliary concentration still leads toactive ingredient contents which are markedly above the activeingredient contents which are achievable by conventional processes.

As expansion element, use can be made in the process according to theinvention of any apparatus which enables sufficiently rapid expansion ofthe liquid/gas solution. Preferably, as expansion element, use is madeof a nozzle, a diffuser, a capillary, an orifice plate, a valve or acombination of the abovementioned expansion elements.

It is important in the process according to the invention that the addedsolid pulverulent auxiliary is mixed with the liquid/gas solutionor—depending on where the pulverulent auxiliary is fed—with thesubstance or mixture of substances to be pulverized. If mixing isinadequate, some of the resulting pulverulent product may not besufficiently stabilized and later melts or fuses together at roomtemperature or at usual ambient temperature.

To achieve good mixing of the auxiliary with the liquid/gas solution orwith the substance or mixture of substances to be pulverized, variouspossible methods are available. Thus, the pulverulent auxiliary can beadded, for example, at the point where the liquid/gas solution exitsfrom the expansion element, that is at or just upstream of the expansionpoint. The auxiliary is then entrained in the free jet formingdownstream of the expansion point, the vigorous and rapid volumeexpansion of the gas present in the liquid/gas solution ensuring anextremely intensive vortexing and mixing of the auxiliary with thesubstance or mixture of substances to be pulverized.

According to another embodiment of the process according to theinvention, the auxiliary is fed in such a manner that it surrounds inthe form of a ring the mass stream exiting from the expansion element inthe area of the outlet point. In other words: the auxiliary is added—forexample by a ring-shaped nozzle—around the free jet exiting from theexpansion element, so that the free jet is in any case initiallysurrounded by the auxiliary. The turbulence occurring on exit of thefree jet from the expansion element ensures good mixing of the auxiliarywith the fine spray of the substance or mixture of substances to bepulverized. Surrounding the free jet with the auxiliary in additionensures that, just after the exit from the expansion element, any liquiddroplets still present cannot be deposited on a surrounding wall, butare entrained. According to a further development of the processaccording to the invention, the mass stream exiting from the expansionelement and the auxiliary are conducted to a type of diffuser, by whichthe divergence of the free jet can be controlled. The diffuser canadditionally have one or more vortex-shedding edges in order to effect astill more intensive mixing between the free jet and the auxiliary bythe turbulence formed there.

In preferred embodiments of the process according to the invention, theliquid/gas solution is expanded into a spray tower. The auxiliary to beadmixed can then, for example, be transported by means of pneumatictransport into the spray tower and added at the desired point.Alternatively, the cold powder can be taken off from the spray tower andmixed in a separate mixer with precooled pulverulent auxiliary at atemperature beneath the melting point of the substance or mixture ofsubstances to be pulverized.

In preferred embodiments of the process according to the invention, inaddition to the gas which is already dissolved in the substance ormixture of substances to be pulverized, further gas is added in the areaof the expansion element, which gas can be termed so-called excess gas.By means of this excess gas, the temperature reached in the expansionprocess may be set more independently. It is not necessary for theliquid/gas solution to be essentially saturated with the gas, nor, forexample, need a relatively high pressure be chosen in order to achieve agas concentration in the liquid which is sufficiently high for thedesired cooling. Rather, the desired cooling in the area of theexpansion point can substantially be effected by the rapid expansion ofthe additionally fed excess gas. Furthermore, there is the possibilityof selecting as excess gas a gas which is different from the gasdissolved in the liquid. For example, the excess gas can be selectedwith regard to a temperature decrease as great as possible, whereas thegas to be dissolved in the liquid is specified according to otheraspects. In addition to improved cooling in the area of the expansionpoint, the excess gas also leads to a still better mixing or vortexingafter the exit of the mass stream from the expansion element and thus tostill smaller powder particles.

Various possibilities exist with respect to feeding the excess gas.According to one embodiment of the process according to the invention,the excess gas is fed into the liquid/gas solution between the pressurevessel and the expansion element, in particular just upstream of theexpansion point. In this case, for improved mixing with the liquid/gassolution, a static mixer can be used, for example.

According to another embodiment, in the expansion element, by means of atwo-component nozzle, the liquid/gas solution and additionally suppliedexcess gas are expanded together with one another. In this embodiment,the excess gas is therefore not added to the liquid/gas solution, but isfed directly to the expansion point, so that the liquid/gas solution andthe pure excess gas are expanded simultaneously. The two-componentnozzle can be, for example, of a type such that the liquid/gas solutionexits through a central channel, whereas the excess gas exits through aring channel which coaxially surrounds the central channel.

According to yet another embodiment, the excess gas together with thesolid pulverulent auxiliary is fed to the solution or the substance ormixture of substances.

When the substance or mixture of substances to be pulverized ismentioned above, this is taken to mean that the liquid to be pulverizedneed not be a pure substance, but it can perfectly well be a mixture orsolution of various liquids or substances, the liquids or substancesbeing able to be either organic or inorganic liquids or substances.Furthermore, a further substance may be added to a liquid puresubstance, which further substance affects the properties of theresulting pulverulent end product in a desired manner. For example, anemulsifier can be added to a water-insoluble liquid to be pulverized inorder in this manner to achieve improved water dispersibility of thepulverulent end product. The liquid substance to be pulverized or themixture of substances can also be a suspension.

With reference to the single figure, an apparatus is described in moredetail below which can be used with advantage for carrying out theprocess according to the invention.

The figure shows, as pressure vessel, an autoclave 10 into which theliquid substance to be pulverized or the mixture of substances ischarged. By suitable measures, for example by agitating the autoclave 10or the autoclave contents, a selected gas is then dissolved underpressure in the liquid introduced. The selected gas is fed in aconventional manner and the feed is not shown in the figure. Toaccelerate the dissolution of gas in the liquid to be pulverized, theliquid and the gas to be dissolved therein can be conducted cocurrentlythrough a static mixer and can then be introduced into the autoclave 10.Depending on the type of gas selected, and depending on the pressureselected and on the temperature, gas concentrations in the liquid phasebetween 1 and 90% by weight, preferably from 5 to 50% by weight, and inparticular from 10 to 40% by weight, can be achieved. The temperature isexpediently in the range of room temperature or ambient temperature, butin the case of high-viscosity substances or mixtures of substances ahigher temperature can be necessary. It is essential that the substanceor the mixture of substances to be pulverized is present as liquid orsuspension in the pressure vessel.

The liquid/gas solution present in the autoclave 10 after dissolution ofthe gas is fed via a line 12 to a three-way valve 14. From a gas vessel16, additional gas, so-called excess gas, is fed via a line 18 to thethree-way valve 14. The excess gas can be a gas other than the gasdissolved in the liquid.

From the three-way valve 14, the liquid/gas solution and the excess gasfed are passed to an expansion element which is here a high-pressurenozzle 20. Between the high-pressure nozzle 20 and the three-way valve14, an additional static mixer can be provided in order to improvemixing of the excess gas into the liquid/gas solution.

The high-pressure nozzle 20 is arranged at the narrowest point of adiffuser 22 which is fixed in the top cover of a spray tower 24. Via afunnel 26 connected to the diffuser 22, a solid pulverulent auxiliary 28is added continuously as long as the liquid/gas solution and the excessgas flow out of the high-pressure nozzle 20. Between the high-pressurenozzle 20 and the inner wall of the funnel 26 or the diffuser 22 isformed an initially contracting and then expanding again ring gapthrough which flows the added auxiliary 28. The auxiliary thereforeannularly surrounds the mass stream flowing out of the high-pressurenozzle 20. The auxiliary 28 can be transported into the funnel 26 byknown methods, for example by pneumatic transport, by shaking rails, bymeans of a screw conveyor, a starwheel feeder or the like.

The great increase in volume of the gas present in the liquid/gassolution and of the additionally fed excess gas after the exit from thehigh-pressure nozzle 20 leads to high turbulence and thus to good mixingof the auxiliary with the mass stream exiting from the high-pressurenozzle 20. In the exemplary embodiment shown, a vortex-shedding edge 30present in the diffuser further increases the turbulence.

The intense cooling which is due to the expansion of the gas dissolvedin the liquid and of the excess gas ensures, together with the highturbulence mentioned, mixing with the auxiliary which is so rapid andintensive that the pulverulent final product wanted is obtained even ata spray tower height of only 1 m. The powder collects in the lower partof the spray tower 24 and can be withdrawn in a conventional manner.

The gas dissolved in the liquid and the excess gas separate, downstreamof the exit from the high-pressure nozzle 20, from the substance ormixture of substances to be pulverized. In the exemplary embodimentshown, the gas released in this manner is taken off in the upper area ofthe spray tower 24 by a line 32. The calming zone present between thediffuser 22 and the spray tower inner wall avoids a discharge of fineparticles through the line 32. Any fine fraction of pulverized productwhich may nevertheless be present in the gas removed by suction maystill be separated off from the gas stream upstream of a suction fandesignated by 34 in a conventional manner, e.g. by means of a cyclonewhich is not depicted here.

Some examples of applications of the process according to the inventionwill now be specified, some of which arose with use of the apparatusdescribed above.

EXAMPLE 1

3 kg of a low-water and low-aroma homogenized liquid pigment concentrate(colour index 130,000), which had been produced from paprika byextraction with hexane, were introduced into the autoclave 10 having avolume of 5 1. Carbon dioxide, at a pressure of 125 bar and atemperature of 32° C. was then run through the liquid for 90 min frombottom to top, in order to saturate the liquid pigment concentrate withthe gas, at least approximately, under the specified conditions.

The carbon dioxide supply was then terminated, the spray line 12 wasopened and the resulting gas-containing solution was expanded through anozzle 20 having an opening diameter of 0.3 mm which was integrated intothe top cover of the spray tower 24. By feeding additional carbondioxide to the gas-containing solution just upstream of the expansionpoint, the temperature in the spray tower was set to −25° C. In theannular space (see diagram) around the nozzle 20, highly dispersesilicon dioxide was added during the spraying operation. After aspraying time of 1 min, 100 g of a homogeneous powder were taken offfrom the spray tower. The content of auxiliary (silicon dioxide) was 30%by weight, and thus that of the active ingredient (pigment concentrate)was 70% by weight. The powder form of the resulting product wasretained, even on warming to a temperature of 35° C. This is notable tothe extent that the starting pigment concentrate is liquid at such atemperature and even on cooling to −18° C., still has a creamyconsistency. By means of the process described, therefore, stabilizationof the powder form is achieved at temperatures which are more than 50°C. above the solidification temperature of the substance to bepulverized in the present example.

EXAMPLE 2

Carbon dioxide at 250 bar and 50° C. was run for 3 hours through thepaprika pigment concentrate described in Example 1. The resultinggas-containing solution was atomized as in Example 1. Feed of carbondioxide just upstream of the expansion point set the temperature in thespray tower to −30° C. Pulverulent polyethylene glycol was added asauxiliary as described in Example 1. After completion of the experiment,200 g of powder having an auxiliary content (polyethylene glycol) of 70%by weight could be withdrawn from the spray tower. The powder form wasretained even on warming to 25° C.

EXAMPLE 3

3 kg of a low-water and low-aroma homogenized pigment concentrate(colour index 80,000) which had been produced from paprika by extractionwith carbon dioxide were placed in the autoclave 10 having a volume of5 1. Carbon dioxide was passed through the liquid from bottom to top ata pressure of 125 bar and a temperature of 32° C. for 90 min. The carbondioxide feed was then terminated and the spray line was opened.

The gas-containing solution was expanded by a nozzle 20 integrated intothe top cover of the spray tower 24 having an opening diameter of 0.5mm. During expansion of the gas-saturated solution, a spray towertemperature of 0° C. was established. During the spraying operation,highly disperse silicon dioxide was metered into the annular space (seediagram) around the nozzle 20. After a spraying time of 1 min, 900 g ofa homogeneous powder were withdrawn from the spray tower. The silicondioxide content was 35% by weight. The powder form was retained even onwarming to a temperature of 35° C.

EXAMPLE 4

42 kg of a commercial paprika extract (colour index 130,000) which hadbeen produced by extraction of paprika powder with hexane wereintroduced into an autoclave having a volume of 400 l. Carbon dioxidewas dissolved in the extract at a pressure of 250 bar and a temperatureof 50° C. The pigment concentrate was then sprayed through a nozzlehaving an opening diameter of 0.8 mm. During the spraying operation,highly disperse silicon dioxide was metered in by a double diaphragmpump operated by compressed air. The auxiliary was added at a point inthe area of the nozzle opening.

55.3 kg of powder having a content of highly disperse silicon dioxide ofapproximately 24% by weight were produced in 38 min at a temperature inthe spray tower of −10° C. The powder remained free-flowing even at roomtemperature.

EXAMPLE 5

300 g of an aroma oil which had been produced from rosemary wereintroduced into an autoclave having a volume of 1 l. Carbon dioxide wasdissolved in the liquid at a pressure of 100 bar and room temperature.The gas-containing solution was expanded into a spray tower through anozzle having an opening diameter of 0.3 mm. The temperature in thespray tower was −5° C. As auxiliary, highly disperse silicon dioxide wasadded to the free jet. A pulverulent solid having an auxiliary content(silicon dioxide) of 25% by weight is obtained. The active ingredientcontent (rosemary) of the resulting powder was thus 75% by weight.

EXAMPLE 6

250 g of an aroma oil which had been produced from rosemary wereintroduced into an autoclave having a volume of 1 l. Carbon dioxide wasdissolved in the liquid at a pressure of 150 bar and a temperature of33° C. The gas-containing solution was fed via a spray line heated to60° C. to a nozzle having an opening diameter of 0.3 mm and expandedinto a spray tower. By metering additional carbon dioxide, a temperatureof −12° C. was established in the spray tower. During the expansion,Palatinit (Isomalt) was added. A pulverulent product having a Palatinitcontent of 87% by weight is obtained.

EXAMPLE 7

300 g of an aroma oil which had been produced from rosemary extract wereintroduced into an autoclave having a volume of 1 l. Carbon dioxide wasdissolved in the liquid at a pressure of 150 bar and a temperature of19° C. The gas-containing solution was fed via a spray line of the sametemperature to a nozzle having an opening diameter of 0.3 mm andexpanded into a spray tower. By metering additional carbon dioxide, atemperature of −18° C. was established in the spray tower. During theexpansion, a mixture of 80% by weight Palatinit (Isomalt) and 20% byweight highly disperse silicon dioxide was added. A pulverulent producthaving an auxiliary (Palatinit+silicon dioxide) content of 50% by weightis obtained.

EXAMPLE 8

280 g of a liquid preparation of a pepper extract were introduced intoan autoclave having a volume of 1 l. The preparation has a piperinecontent of 40% by weight, an aroma oil content of 10% by weight and anemulsifier content of 15% by weight. Carbon dioxide was dissolved in theliquid at a pressure of 70 bar and a temperature of 42° C. Thegas-containing solution was fed via a spray line of the same temperatureto a nozzle having an opening diameter of 0.3 mm and expanded into aspray tower. By metering additional carbon dioxide, a temperature of−14° C. was established in the spray tower. During the expansion, highlydisperse silicon dioxide was added. A pulverulent free-flowing producthaving an auxiliary (silicon dioxide) content of 39% by weight isobtained.

EXAMPLE 9

270 g of a liquid preparation of a pepper extract were introduced intoan autoclave having a volume of 1 l . The preparation has a piperinecontent of 40% by weight, an aroma oil content of less than 5% by weightand an emulsifier content of 15% by weight. Carbon dioxide was dissolvedin the liquid at a pressure of 110 bar and a temperature of 42° C. Thegas-containing solution was fed via a spray line of the same temperatureto a nozzle having an opening diameter of 0.3 mm and expanded into aspray tower. By metering additional carbon dioxide, a temperature of −4°C. was established in the spray tower. During the expansion, highlydisperse silicon dioxide was added. A pulverulent free-flowing producthaving an auxiliary (silicon dioxide) content of 21% by weight isobtained.

EXAMPLE 10

290 g of a celery extract which is mobile at room temperature wereintroduced into an autoclave having a volume of 1 l. Carbon dioxide wasdissolved in the liquid at a pressure of 160 bar and a temperature of42° C. The gas-containing solution was fed via a spray line of the sametemperature to a nozzle having an opening diameter of 0.3 mm andexpanded into a spray tower. By metering additional carbon dioxide, atemperature of 5° C. was established in the spray tower. During theexpansion, highly disperse silicon dioxide was added. A pulverulentfree-flowing product having an auxiliary (silicon dioxide) content of35% by weight is obtained.

What is claimed is:
 1. A process for producing a pulverulent productfrom at least one substance at room temperature, having the steps of:providing, in a pressure vessel, the at least one substance to bepulverized; dissolving a gas in the at least one substance underelevated pressure to produce a liquid/gas solution; conducting theliquid/gas solution out of the pressure vessel to an expansion element;and passing the liquid/gas solution through the expansion element forrapid expansion of the solution, wherein a solid, pulverulent auxiliaryis admixed to an ingredient selected from the group consisting of the atleast one substance and the liquid/gas solution.
 2. The processaccording to claim 1, wherein the expansion process taking place duringpassage of the liquid/gas solution through the expansion element iscarried out in such a manner that the temperature roughly attains orfalls below the solidification temperature of the at least onesubstance.
 3. The process according to claim 1, wherein gas is dissolvedin the at least one substance until the at least one substance isessentially saturated with the gas.
 4. The process according to claim 1,wherein the gas is at least one gas selected from the group consistingof carbon dioxide, hydrocarbons, halogenated hydrocarbons, ethers, inertgases, gaseous oxides and ammonia.
 5. The process according to claim 1,wherein the elevated pressure under which the gas is dissolved in the atleast one liquid substance is in the range from 5 bar to 800 bar.
 6. Theprocess according to claim 1, wherein the dissolution of the gas in theat least one substance is accelerated by mixing the gas with the atleast one substance.
 7. The process according to claim 6, wherein thegas is mixed with the at least one substance by at least one techniqueselected from the group consisting of static mixing, shaking thepressure vessel, rolling the pressure vessel, stirring the solutionforming in the pressure vessel, recirculating the liquid phase presentin the pressure vessel and recirculating the gas phase present in thepressure vessel.
 8. The process according to claim 1, wherein theparticle size of the pulverulent auxiliary is less than 100 μm.
 9. Theprocess according to claim 1, wherein at least one ingredient isselected from the group consisting of starch, modified starch, commonsalt, sugar, proteins, gelatin, titanium dioxide, magnesium stearate,polyglycols, highly dispersed silicon dioxide, silicic acid, bentonite,lime, glutamate, emulsifiers, phospho-lipids, partial glycerides, fats,cellulose, cellulose derivatives, polylactic acid, waxes, dextrin,kaolin, zeolites, thickeners, alginates, pectin, activated carbon andvery finely ground plant components.
 10. The process according to claim1, wherein the auxiliary concentration, based on the total amount of theat least one substance and auxiliary, is between 1% by weight and 90% byweight.
 11. The process according to claim 1, wherein the expansionelement comprises at least one device selected from the group consistingof a nozzle, a diffuser, a capillary, an orifice plate and a valve. 12.The process according to claim 1, wherein the auxiliary is fed to theliquid/gas solution at the point where the liquid/gas solution exitsfrom the expansion element.
 13. The process according to claim 1,wherein the solution is expanded into a spray tower.
 14. The processaccording to claim 1, wherein gas is additionally fed into theliquid/gas solution between the pressure vessel and the expansionelement.
 15. The process according to claim 1, wherein the liquid/gassolution and additionally supplied gas are expanded together with oneanother in the expansion element by means of a two-component nozzle. 16.The process according to claim 1, wherein additional gas is also fedtogether with the feed of the solid pulverulent auxiliary to aningredient selected from the group consisting of the at least onesubstance and the liquid/gas solution.
 17. The process according toclaim 1, wherein the solid, pulverulent auxiliary is admixed to the atleast one substance upstream of the expansion element.
 18. The processaccording to claim 1, wherein the solid, pulverulent auxiliary isadmixed to the liquid/gas solution upstream of the expansion element.19. The process according to claim 1, wherein the solid, pulverulentauxiliary is admixed to the liquid/gas solution in the expansionelement.
 20. The process according to claim 1, wherein the solid,pulverulent auxiliary is admixed to the liquid/gas solution downstreamof the expansion element.